This invention relates to, e.g., determining the activation potential of blood platelets and, specifically, the reactivity of platelets to .alpha.-thrombin.
Upon becoming activated, human blood platelets undergo changes in platelet surface membrane receptors, which may result in platelet aggregation, interaction with fibrin fibers, and the resulting formation of a thrombus. In certain disease states, e.g., coronary artery disease and diabetes, platelets may exist in a hyperreactive state, resulting in increased risk to the patient of thrombosis. Early detection of platelet hyperreactivity can permit the timely administration of antiplatelet drugs.
.alpha.-thrombin is considered the most physiologically important activator of platelets. Quantitative determination of thrombin-induced changes in specific receptors, as measured by monoclonal antibody binding, has been carried out in assays performed on washed and resuspended platelets. Activation of platelets by adenosine diphosphate and epinephrine has been measured in a whole blood assay by flow cytometry.
It is known that the tetrapeptide glycyl-L-prolyl-L-arginyl-L-proline (GPRP), an analog of the amino terminus of the .alpha.-chain of fibrinogen and the fibrin monomer, binds to fibrinogen and, under some experimental conditions, inhibits fibrin polymerization.